View source for HMS Graph

{{short description|German World War II submarine captured by the Royal Navy}}
{{Use dmy dates|date=July 2019}}
{{EngvarB|date=July 2019}}

{|{{Infobox ship begin}}
{{Infobox ship image
|Ship image=U 570.jpg
|Ship image size=300px
|Ship caption=HMS ''Graph'' in 1943
}}
{{Infobox ship career
|Hide header=
|Ship country=[[Nazi Germany]]
|Ship flag={{shipboxflag|Nazi Germany|naval}}
|Ship name=''U-570''
|Ship ordered=24 October 1939
|Ship builder=[[Blohm & Voss]], [[Hamburg]]
|Ship yard number=546
|Ship laid down=21 May 1940
|Ship launched=20 March 1941
|Ship commissioned=15 May 1941
|Ship captured=Captured by the [[Royal Navy]] on 27 August 1941
|Ship notes=
}}
{{Infobox ship career
|Hide header=title
|Ship country=United Kingdom
|Ship flag={{shipboxflag|United Kingdom|naval}}
|Ship name=HMS ''Graph''
|Ship namesake=[[Graph of a function|Graph]]<ref name="Terrell144">Terrell (1958), p.144</ref>
|Ship acquired=27 August 1941
|Ship commissioned=5 October 1941<ref name="uboatnetgraph" />
|Ship decommissioned=21 June 1943
|Ship fate=*Ran aground on 20 March 1944
*Scrapped in 1961
|Ship notes=
}}
{{Infobox ship characteristics
|Hide header=
|Header caption=
|Ship class=[[German Type VII submarine#Type VIIC|Type VIIC]] [[submarine]]
|Ship displacement=
*{{convert|769|t|LT|0|lk=on}} surfaced
*{{convert|871|t|LT|0|abbr=on}} submerged
|Ship length={{convert|67.10|m|ftin|abbr=on}}
|Ship beam={{convert|6.20|m|ftin|abbr=on}}
|Ship draught={{convert|4.74|m|ftin|abbr=on}}
|Ship propulsion=
*Two Blohm and Voss Diesel engines, {{convert|1440|PS|kW+shp+kW}} each<ref>Report On The German Submarine U-570 Class p.52</ref>
*One 465 kW electric motor and one 276 kW electric motor<ref>Report On The German Submarine U-570 Class p.53</ref>
|Ship speed=
*{{convert|17.7|kn|lk=in}} surfaced
*{{convert|7.6|kn}} submerged
|Ship range={{convert|8,500|nmi|abbr=on}}
|Ship test depth={{convert|230|m|ft|abbr=on}}
|Ship complement=
|Ship sensors=
|Ship EW=
|Ship armament=
*5 × {{convert|53.3|cm|in|0|abbr=on}} [[torpedo tube]]s (four bow, one stern)
*14 × [[torpedo]]es ''or'' 26 TMA [[Naval mine|mine]]s
*1 × [[8.8 cm SK C/35 naval gun|{{convert|8.8|cm|in|2|abbr=on}} deck gun]] (220 rounds)
*various AA guns
}}
{{Infobox service record
|is_ship=yes
|label=Service record (''Kriegsmarine'')<ref name="uboatnetu570" />
|partof=
*[[3rd U-boat Flotilla]]
*15 May – 27 August 1941
|codes=M 42 381
|commanders=
*''[[Kptlt.]]'' Hans-Joachim Rahmlow
*15 May – 27 August 1941
|operations=*1 patrol:
*23 – 29 August 1941
|victories=None
}}
{{Infobox service record
|is_ship=yes
|label=Service record (''Royal Navy'')<ref name="uboatnetgraph">{{cite web
 |url=https://uboat.net/allies/warships/ship/7751.html
 |title=HMS Graph (P 715)
 |last=Helgason
 |first=Guðmundur
 |website=German U-boats of WWII - uboat.net
 |access-date=25 September 2011
}}</ref>
|partof=
|codes=
|commanders=
*''[[Lieutenant (navy)|Lt.]]'' George Robson Colvin
*31 August – 10 October 1941
*''Lt.'' [[Edward Dudley Norman]]
*10 October 1941 – 1 June 1942
*''Lt.'' Peter Barnsley Marriott
*1 June 1942 – 2 April 1943
*''Lt.'' David Swanston
*3 April – 21 June 1943
|operations=
|victories=
}}
|}

'''HMS ''Graph''''' ([[pennant number]] P715) was a German [[German Type VII submarine#Type VIIC|Type VIIC]] [[U-boat]] captured and recommissioned by the British [[Royal Navy]] during [[World War II]].

Commissioned as '''''U-570''''' in [[Nazi Germany]]'s ''[[Kriegsmarine]]'' in mid-1941, she was attacked and captured on her first patrol. She provided the Royal Navy and [[United States Navy]] with useful information about German submarines. Refitted for use by the Allies, she carried out three combat patrols with a Royal Navy crew, becoming the only U-boat to see active service with both sides during the war. She was withdrawn from service in 1944 due to problems maintaining her. While being towed to the breakers for scrapping, she ran aground on the [[Isle of Islay]], off the west coast of [[Scotland]]. Some of the wreckage was removed as scrap but some remains to the present day.

==Design and construction==
The submarine was built to the [[German Type VII submarine#Type VIIC|German Type VIIC]] design. She had a [[displacement (ship)|displacement]] of {{convert|769|t|LT|0}} when surfaced, and {{convert|871|t|LT|0|abbr=on}} when submerged. The boat was {{convert|67.10|m|ftin}} long, with a beam of {{convert|6.2|m|ftin}}, and a draught of {{convert|4.74|m|ftin}}. The [[Diesel-electric transmission|diesel-electric]] propulsion system provided a maximum speed of {{convert|18.8|kn|lk=in}} surfaced or {{convert|7.6|kn}} submerged. The ''U-570'' had a fuel capacity of {{convert|109|LT|MT}} which gave a range of {{convert|7500|nmi|abbr=on}} at {{convert|10|kn}}.<ref>CB 4318 p. 4</ref> The [[test depth]] of the submarine was {{convert|230|m}}.<ref name="macintrie" />

Her main armament consisted of five 53.3-cm (21-inch)  torpedo tubes; four in the bow, and a fifth in the stern. She could carry a total of 14 torpedoes – five in the torpedo tubes, seven reloads inside the pressure hull, and a further two in water-tight canisters outside the pressure hull.<ref name="CB4318-5" /> The boat was fitted with an [[8.8 cm SK C/35 naval gun|8.8-cm C/35]] [[deck gun]] (with around 150 rounds of ammunition), and a [[2 cm Flak 30/38/Flakvierling|2-cm Flak 30]] anti-aircraft gun<ref name="CB4318-5" /> with a 28-cm [[stereoscopic rangefinder]].<ref name="CB4318-26">CB 4318 p. 26</ref> She also carried several machine guns.<ref name="CB4318-5">CB 4318 p. 5</ref>

[[Blohm & Voss]] [[Keel laying|laid down]] ''U-570'' at [[Hamburg]] on 21 May 1940. The submarine was [[Ceremonial ship launching|launched]] on 20 March 1941.<ref name="uboatnetu570">{{cite web
 |url=https://uboat.net/boats/u570.htm
 |title=The Type VIIC Uboat U-570
 |last=Helgason
 |first=Guðmundur
 |website=German U-boats of WWII - uboat.net
 |access-date=25 September 2011
}}</ref>

==Kriegsmarine service==
''U-570'' was [[Ship commissioning|commissioned]]  into the ''Kriegsmarine'' on 15 May 1941.<ref name="uboatnetu570" /> After a series of short testing and commissioning trips in the Baltic, she moved to Norway where she carried out short training voyages and fired practice torpedoes. By 25 July, she had moved to the [[German U-boat bases in occupied Norway|German U-boat base at Lofjord]],<ref>CB 4051, p. 4</ref> part of [[Trondheimsfjord]], around {{convert|13|km|nmi|0}} north of Trondheim.

In late August 1941, [[B-Dienst]] (the German naval codebreaking organisation) became aware of a large concentration of Allied merchant ships in the region of the North Atlantic south of Iceland. Admiral [[Karl Dönitz]] ordered 16 U-boats to the area.<ref>Blair 1996, p. 340</ref> ''U-570'' was to be one of these and, on the morning of 24 August, she put to sea on her first war patrol. Her planned mission was to patrol the area south of Iceland before proceeding to the U-boat base at [[La Pallice]], France. She carried provisions for four weeks at sea.<ref>CB 4051, p. 5</ref>

''Kapitänleutnant'' Hans-Joachim Rahmlow commanded ''U-570''. He was an experienced naval officer, but had only recently transferred to U-boats, having previously been a gunnery and coastal defence specialist.<ref name="cb4061page2">CB 4051, p. 2</ref> He had commanded the training submarine {{GS|U-58|1939|2}}, but had carried out no war patrols. Likewise, the First Watch Officer (second-in-command) had only served a few months with the U-boat branch, after serving on destroyers, and the Second Watch Officer had little experience, having only recently been commissioned. The engineer was the only officer (and one of only four crewmen) who had served on a U-boat war patrol. While the boat's petty officers had several years of navy service, many of the enlisted crew were still new to the German navy and had only a few months of U-boat training.<ref name="cb4061page2" />

''U-570''{{'}}s inexperienced crew was not unique for the time. British interrogation of rescued crew-members of {{GS|U-501||2}}—sunk on her first patrol in September 1941—revealed that 41 out of 48 crew were on their first war patrol.<ref>Blair 1996, p. 362</ref>

==Capture==

{{OSM Location map
| coord = {{Coord|59|40|00|N|13|00|00|W}}
| zoom = 4
| float = right
| width = 220
| height = 290
| title =
| mark-size = 9
| label =
| mark-coord = {{Coord|62|15|00|N|18|35|0|W}}
| label-pos = right
| label-size = 10
| label-color =
| mark-title =
| mark-image =
| mark-description =
|caption = Location of the capture, south of Iceland
}}

On 27 August 1941, ''U-570'' spent much of the morning submerged. She had been four days at sea and this was to give respite to a crew that was suffering acutely from [[seasickness]] (several had been incapacitated). Earlier that morning, a [[Lockheed Hudson]] bomber of [[No. 269 Squadron RAF|269 Squadron, RAF]], flown by Sergeant Mitchell and operating from [[Kaldaðarnes]], Iceland, had attacked her. The attack failed when the Hudson's bomb-racks failed to release its [[depth charges]].<ref name="conyers-nesbit" /> ''U-570'' surfaced at position {{coord|62|15|N|18|35|W}} at around 10:50 am, immediately below a second 269 Squadron Hudson, flown by Squadron Leader James Thompson. Thompson was patrolling the area after Mitchell summoned him by radio.<ref>
{{cite journal
| last =Thomas
| first =Andrew
| date =24 May 2001
| title =Icelandic Hunters – No 269 Squadron Royal Air Force
| journal=Aviation News
| publisher=HPC Publishing
| location=St Leonards-on-Sea, East Sussex
| url  =http://www.oca.269squadron.btinternet.co.uk/history/icelandic_hunters/aviation_news.pdf
| access-date=2009-09-13
|archive-url=https://web.archive.org/web/20110610231043/http://www.oca.269squadron.btinternet.co.uk/history/icelandic_hunters/aviation_news.pdf|archive-date=2011-06-10}}</ref> Rahmlow, who had climbed out onto the bridge, heard the approaching Hudson's engines and ordered a crash-dive. Thompson's aircraft reached ''U-570'' before she was fully submerged and dropped its four {{convert|250|lb|kg|-1|adj=on}} [[depth charges]]—one detonated just {{convert|10|yd|m|-1}} from the boat.<ref name="cb4061page6">CB 4051, p. 6</ref>

''U-570'' quickly resurfaced and around 10 of the crew emerged. The Hudson fired on them with machine guns, but ceased when the U-boat crew displayed a [[white flag|white sheet]]. The captured crew members later recounted to British naval intelligence interrogators what had happened—the depth charge explosions had almost rolled the boat over, knocked out all electrical power, smashed instruments, caused water leaks, and contaminated the air on the boat. The inexperienced crew believed the contamination to be [[chlorine]], caused by acid from [[Battery leakage|leaking]] battery cells mixing with sea-water, and the engine-compartment crew panicked and fled forward to escape the gas. Restoring electrical power—for the underwater electric motors and for lighting—would have been straightforward, yet there was nobody remaining in the engine compartment to do this.<ref name="blair342">Blair 1996, p. 342</ref> The submarine was dead in the water and in darkness. Rahmlow believed the chlorine would make it fatal to stay submerged so he resurfaced. The sea was too rough for the crew to man their anti-aircraft gun so they displayed a white flag to forestall another, probably fatal, depth charge attack from the Hudson—they were unaware the aircraft had dropped all its depth charges.

Most of the crew remained on the deck of the submarine as Thompson circled above them, his aircraft now joined by a second Hudson that had been en route from Scotland to Iceland and had broken off its journey to lend assistance.<ref group="Note">The Imperial War Museum's collection includes a [http://www.iwm.org.uk/collections/item/object/80023721 recorded interview] of former RAF Flying Officer Hugh Eccles, who was one of the crew of this aircraft.</ref> A radio request for help saw a [[Consolidated PBY Catalina|Consolidated Catalina]] flying boat of [[No. 209 Squadron RAF|209 Squadron]]<ref group="Note">The aircraft was Catalina number ''AH553'', flown by Flying Officer Edward Jewiss; see; Conyers Nesbit (2008), p.74. Jewiss had been partially responsible for sinking the {{GS|U-452||2}} two days earlier. See: Blair (1996), p.342.</ref><ref name="conyers-nesbit">Conyers Nesbit 2008, p.74</ref> being scrambled at [[Reykjavík]]; it reached the scene three hours later.<ref name="conyers-nesbit" /> The German crew radioed their situation to the German naval high-command, destroyed their radio, smashed their [[Enigma machine]], and dumped its parts overboard along with the boat's secret papers.<ref>CB 4051, p. 7</ref> Admiral Dönitz later noted in his war diary that he ordered U-boats in the area to go to ''U-570''{{'}}s assistance after receiving this report;<ref>Sebag-Montefiore p. 161</ref> {{GS|U-82|1941|2}} responded, but Allied air patrols prevented ''U-82'' from reaching ''U-570''.<ref name="blair342" />

[[File:U570 captutr.jpg|thumb|alt=An aerial photograph of a surfaced submarine in choppy sea; a small ship is close by and both appear to be stationary. Part of the aircraft's left wing can be seen, with a bomb hanging from it.|''U-570'' with one of the Royal Navy trawlers, photographed from an RAF Catalina]]
''U-570''{{'}}s transmission was in plain language and the British intercepted it. Admiral [[Percy Lockhart Harnam Noble|Percy Noble]], commander of [[Western Approaches Command]], immediately ordered several ships to race to the scene.<ref name="blair342" /> By early afternoon, fuel levels had forced the Hudsons to return to Iceland.{{refn|Upon his return to Kaldaðarnes, Thompson wrote off his Hudson in a landing accident, but without serious injury to any on board.<ref>Blair (2006)</ref>|group=Note}} The Catalina, a very long-range aircraft, was ordered to watch the submarine until Allied ships arrived. If none came before sunset, the aircraft was to warn ''U-570''{{'}}s crew to take to the water, then sink her.<ref>{{cite web | title=AIR 41/47—''The RAF in Maritime War – The Atlantic and Home Waters: Vol. III The Preparative Phase July 1941 – Feb 1943.'' | publisher=[[Air Historical Branch]]: Narratives and Monographs, in [[The National Archives (United Kingdom)|The National Archives]]| year=1954 |url=https://www.nationalarchives.gov.uk/catalogue/externalrequest.asp?requestreference=AIR41/47}}</ref> The first vessel to reach ''U-570'', the [[Naval trawler|anti-submarine trawler]] HMT ''Northern Chief'', arrived around 10:00&nbsp;pm, guided to the scene by flares the Catalina dropped. The Catalina returned to Iceland after having circled ''U-570'' for 13 hours.<ref name="blair342" />

The German crew remained on board ''U-570'' overnight; they made no attempt to scuttle their boat as ''Northern Chief'' had signalled she would open fire and not rescue survivors from the water if they did this. (''Northern Chief''{{'}}s captain, N.L. Knight, had been ordered to prevent the submarine from being scuttled by any means.<ref name="blair342" />) During the night, five more Allied vessels reached the scene: the armed trawler ''Kingston Agate'', two anti-submarine whalers,<ref group="Note">The lake-class armed whalers HMS ''Wastwater'' and HMS ''Windermere''</ref> the Royal Navy destroyer {{HMS|Burwell|H94|6}}, and the Canadian destroyer {{HMCS|Niagara|I57|6}}.

At daybreak, the Allies and Germans exchanged [[signal lamp]] messages, with the Germans repeatedly requesting to be taken off as they were unable to stay afloat, and the British refusing to evacuate them until the Germans secured the submarine and stopped it from sinking—the British were concerned that the Germans would deliberately leave behind them a sinking U-boat if they were evacuated. The situation became more confused when a small float-plane appeared: a [[Northrop N-3PB]] of [[No. 330 Squadron RNoAF|330 (Norwegian) Squadron]]).<ref name="dunmore129">Dunmore, p. 129</ref> Unaware of the surrender, it attacked ''U-570'' with small bombs and fired on ''Northern Chief'', which fired back.<ref>Blair 1996, p. 344.</ref> No damage was done and ''Burwell'' ordered the aircraft away by radio.

The weather worsened; several attempts to attach a tow-line to ''U-570'' were unsuccessful. Believing the Germans were being obstructive, ''Burwell's'' captain, S.R.J. Woods<ref>Dunmore, p. 128</ref> ordered a machine gunner to fire warning shots, shots that accidentally hit and slightly wounded five of the German crew.<ref name="dunmore129" /> With much difficulty, an officer<ref group="Note">Lieutenant H.B. Campbell, ''see Conyers Nesbit 2008, p.75'', ''Blair 1996, p. 344''</ref> and three sailors from ''Kingston Agate'' reached the submarine using a [[Carley float]] (a liferaft). After a quick search failed to find the U-boat's Enigma machine, they attached a tow line and transferred the five wounded men and the submarine's officers to ''Kingston Agate''.<ref name="dunmore129" /> The remaining crew were taken on board HMCS ''Niagara'', which by this time had come alongside ''U-570''.<ref name="dunmore129" />

The ships began slowly sailing to Iceland with ''U-570'' under tow, and with a relay of Hudsons and Catalinas constantly patrolling overhead. They arrived at dawn on 29 August at [[Þorlákshöfn]]. There, they beached ''U-570'' as she had been taking on water and was thought to be in danger of sinking.

===Salvage and repair===
Two days after ''U-570''{{'}}s arrival, a British submarine commander—Lieutenant George Robson Colvin—together with a team of engineering warrant officers and civilian technical experts, arrived at Þorlákshöfn from Britain. They then carried out the initial examination and salvage of ''U-570''.

{{blockquote|The submarine was then lying broadside on to the surf and listing heavily to starboard... The interior of the submarine was unlit and was in a chaotic state; leaks of oil and water from the broken gauge glasses of internal tanks had combined with vast quantities of provisions, flour, dried peas and beans, soft fruit, clothes, bedding, and the remains of scores of loaves of black bread to form a revolting morass that in places was knee-deep. It was subsequently discovered that in this ship the crew's W.C. had been converted into a food locker and overturned buckets of excrement added to the general noisome conditions.|Lieutenant GR Colvin, RN|''Ex-German Submarine "U 570" – Report of Proceedings'' (3 October 1941)<ref name=cb4318-p50 />}}

Colvin's team was able to restore lighting and buoyancy; a refloated ''U-570'' was towed around the coast to the British naval base at [[Hvalfjörður]]. There ''U-570'' was docked to the [[depot ship]] HMS ''Hecla'' for repair, with the aim that ''U-570'' could make the trip to Britain under her own power.<ref name=cb4318-p50>CB4318, Appendix 1, p. 50</ref>

The British discovered that the depth charge damage to the U-boat was not critical—there were leaks in some of the ballast tanks and a small leak in a fuel tank. Around one third of the battery cells were cracked and the bow had been buckled. Water had leaked in through a valve that had been unseated by the explosions and through glass gauges that had broken; other damage was minor and no evidence of chlorine gas found. In his report, Colvin stated his opinion that there was no evidence of any [[Damage control (maritime)|damage control]] being carried out and that an experienced submarine crew would have been easily able to improvise repairs, stay submerged and likely evade the air-attack.<ref>CB4318, Appendix 1, p. 52</ref> After their surrender, the German crew had attempted to destroy instruments and fittings, but, with the exception of the wrecked radio and the damaged torpedo firing computer, the attempt appeared half-hearted and the damage was not significant. Also, useful papers had missed destruction. Copies of encrypted signals and their corresponding, plain-language, German texts were found—material of use to the British [[Cryptanalysis of the Enigma|Enigma code breaking]] effort.<ref name="Enigmabattle162">Sebag-Montefiore p. 162</ref> A significant discovery was the U-boat commander's handbook, which provided context and background information for decrypted messages.<ref name="Mallmann" /> The British, unfamiliar with German naval procedures, abbreviations and jargon, had often found German naval traffic hard to understand even when decrypted.

''U-570'' spent three weeks at Hvalfjörður, being repaired and taking short sea trials to test the engines and steering. Between 23 and 26 September, she was carefully inspected by two US Navy officers who had been sent from the United Kingdom to Iceland for that purpose;<ref>Report On The German Submarine U-570 Class p.1</ref> one of the submarine's [[G7a torpedo]]es was off-loaded, handed over to the Americans, and later sent to the United States.<ref>CB4318, Appendix 1, p. 51</ref> An eyewitness recalled that at one point, a Hudson bomber flew low over ''U-570'' and HMS ''Hecla'', signalling with a Morse lamp, "This ****** is mine."<ref>
{{cite web |author=Ross, Bill|title=The Whole Truth | url=https://www.bbc.co.uk/history/ww2peopleswar/stories/99/a6589399.shtml|date=1 November 2005 |work=[[WW2 People's War]] |publisher=BBC |access-date=14 September 2009}}</ref>

[[File:German U-Boat U-570 enters dock at Barrow-in-Furness after her capture.jpg|thumb|right|alt=A surfaced submarine is slowly sailing into a port. A wharf can be seen in the background with large cranes, buildings and two berthed ships.|The ''U-570'' arrives at [[Barrow-in-Furness]], 3 October 1941]]
On 29 September, the submarine set out for the UK, manned by a Royal Navy [[prize crew]] under the command of Lieutenant Colvin.<ref name="times" /> Escorted by the [[S-class destroyer (1917)|S class destroyer]] HMS ''Saladin'' and HMS ''Kingston Agate'', she sailed on the surface as her diving planes had been damaged by the beaching at Þorlákshöfn.<ref>Report On The German Submarine U-570 Class pp. 8–9</ref> Her arrival at [[Barrow-in-Furness]] on 3 October was filmed by [[Pathé News]] newsreel cameras,<ref>
{{cite video
 |date  =1941-10-09
 |title  =His Majesty's U-Boat
 |url   =http://www.britishpathe.com/record.php?id=10607
 |medium =Motion picture
 |publisher=British Pathé
 |location=London
 |access-date=2009-09-13
 |id   =1133.07
}}
</ref> and reported in the press.<ref name="times">
{{cite newspaper The Times|title=Captured U-Boat in Port—British Crew Bring Home Aircraft's Prize |department=News |page=4|issue=49048 |column=C }}
</ref> The capture would later be featured in British propaganda.<ref>
{{cite web
| title  =A Grã-Bretanha Defensora da Liberdade [Great Britain, Defender of Liberty]
| url   =http://vads.ac.uk/large.php?uid=34008&sos=3
| work   =Imperial War Museum: Posters of Conflict
| publisher=Visual Arts Data Services
| format  =Poster
| access-date=2009-09-25
}}</ref> The capture of several other U-boats, such as the {{GS|U-110|1940|2}}, which had sunk whilst under tow, was kept secret to conceal the seizure of their code-books and [[Enigma machine]]s. ''U-570''{{'}}s situation had been reported to the German high command. Also, so many ships, aircraft, and personnel had been involved in her capture that any attempt at secrecy would have been futile.

''U-570'' was placed in a dry-dock in the [[Vickers Shipbuilding and Engineering|Vickers]] shipyard in Barrow. Her repair was complicated by depth-charge damage to her bow—her plating had been buckled, trapping four electrically powered [[torpedo]]es in their torpedo tubes. Two officers from the Royal Navy's Department of Torpedoes and Mines Investigations had the task of retrieving them for examination. The dock was evacuated while a volunteer shipyard worker cut the armed torpedoes free with an [[Oxy-fuel welding and cutting|oxyacetylene cutter]] under the officers' supervision. One of the officers—Lt Martin Johnson—then removed the [[magnetic pistol]]s (detonators) from the torpedoes and made them safe—a dangerous task as the pistols were sensitive mechanisms and large enough to produce a lethal explosion on their own. For this act he was awarded the [[George Medal]] on 8 December 1942.<ref name="JohnsonObit">
{{cite news | title= Lt-Cdr Martin Johnson | work=The Times | date=2004-07-28|url=http://www.timesonline.co.uk/tol/comment/obituaries/article462336.ece}}{{dead link|date=September 2024|bot=medic}}{{cbignore|bot=medic}}
</ref><ref>{{London Gazette|issue=35815 |supp=y|page=5345|date=1942-12-04}}</ref>

Squadron Leader Thompson, his navigator/bomb-aimer—[[Flying Officer]] John Coleman, and Flying Officer Edward Jewiss (the pilot of the 209 Squadron Catalina), all received the [[Distinguished Flying Cross (United Kingdom)|Distinguished Flying Cross]] on 23 September 1941.<ref>{{London Gazette|issue=35283|page=5521| date=23 September 1941}}</ref><ref>{{London Gazette|issue=35283|page=5522| date=23 September 1941}}</ref> The captain of ''Kingston Agate'', Henry L'Estrange, was awarded the [[Distinguished Service Cross (United Kingdom)|Distinguished Service Cross]] for his part in the capture.<ref>{{London Gazette|issue=35586|page=2507|date=5 June 1942}}</ref><ref>{{cite web |url=http://www.historicalrfa.org/commodore-henry-owen-lestrange-dsc-rd-rnr |title=Commodore Henry Owen L'Estrange, DSC, RD, RFA |author=Christopher J White, Peter Robinson |work=Heroes of the RFA|publisher=www.historicalrfa.org |access-date=29 May 2011}}</ref>

===German response===
Initially, all the German naval high command knew of ''U-570''{{'}}s situation was her radio message, saying she was under air-attack and unable to submerge; they only learned of her capture from later British press reports. They were concerned for the security of their communications and ''[[Vizeadmiral]]'' [[Erhard Maertens]], the Director of the Naval Intelligence Command,  was ordered to report on this. He concluded that in the worst-case scenario—that is, the British had secured ''U-570''{{'}}s codebooks and Rahmlow had revealed to them his memorised, secret keyword—communications would be compromised until a new list of Enigma machine settings came into force in November. However, he believed this worst case to be unlikely and that ''U-570''{{'}}s crew would have almost certainly destroyed their secret material. Even if they had not, the additional security of the commander's secret keyword would defeat British cryptanalysis.<ref name="Enigmabattle163">Sebag-Montefiore p. 163</ref>

In fact, the British code-breakers at [[Bletchley Park]] found the extra security of the keyword procedure to be simply of "nuisance value".<ref name="Enigmabattle164">Sebag-Montefiore p. 164</ref> ''U-570''{{'}}s crew had indeed destroyed their Enigma machine and code-books but the Germans were unaware of the Royal Navy's earlier capture of {{GS|U-110|1940|2}}'s secret material, thanks to which the British had been breaking German naval cyphers since June 1941. British code-breaking was not seriously impeded until February 1942, when a new naval Enigma cypher remained unbroken for 10 months—the so-called "Shark Blackout".

Apart from Rahmlow, ''U-570''{{'}}s officers were taken to an officers' prisoner-of-war camp at [[Grizedale Hall]] in [[Cumbria]].<ref name="blair347">Blair 1996, p. 347.</ref> This was nicknamed ''U-boat Hotel'' by the British as, during the early part of the war, the majority of prisoners were naval officers rescued from sunken U-boats.<ref name="bblm">{{cite web|url=http://www.bbm.org.uk/GrizedaleHall.htm|title=Grizedale Hall Prisoner-of-War Camp|publisher=The Battle of Britain London Monument|access-date=4 February 2010|url-status=dead|archive-url=https://web.archive.org/web/20110927230738/http://www.bbm.org.uk/GrizedaleHall.htm|archive-date=27 September 2011}}</ref> There, a "[[Court of Honor|Court of Honour]]" convened by other German prisoners, including captured U-boat ace [[Otto Kretschmer]], tried Rahmlow, ''in absentia'', and ''U-570''{{'}}s other officers. Rahmlow and his second-in-command, Bernhard Berndt, were found "guilty of cowardice"; the other two officers were "acquitted". On the night of 18/19 October, Berndt escaped from the camp. A detachment of the [[Home Guard (United Kingdom)|Home Guard]] apprehended him, shooting him when he tried to escape.<ref name="Enigmabattle162" />

According to some sources, he had escaped from the camp with the stated intention of redeeming himself by making his way to ''U-570''{{'}}s dockyard at Barrow–a distance of only {{convert|22|mi|km}}–and somehow destroying her.<ref name="Enigmabattle162" /><ref name="blair347" /> Another source states he was forced to make an escape attempt by a group of senior German prisoners who enforced a brutal regime of punishing those who held anti-Nazi views or who co-operated with the British, and that Berndt only broke away and ran from the Home Guard when he realised they were returning him to Grizedale Hall; they shot him dead after he ignored warning shots.<ref name="gotaway">{{cite book | title=The One That Got Away | last1=Burt | first1=Kendal | last2=Leasor | first2=James | year=2006 | chapter=Chapter 4 | publisher=Pen & Sword Military | isbn=1-84415-437-8}}
</ref> The British placed Rahmlow in a camp with German Army and Air Force prisoners to avoid further incidents of this kind.<ref group="Note">These events may have formed the basis for the 1970 film ''[[The McKenzie Break]]'', in which a German PoW, played by Horst Janson, is victimised by his fellow prisoners in a Scottish PoW camp, while others escape and are subsequently recaptured.</ref>

The German high command recognised ''U-570''{{'}}s loss could be partially blamed on the crew's lack of training and experience (during the early part of the war, U-boat training had been cut down to two months).<ref name="mulligan79">Mulligan (2011), p.79</ref> Both this and mounting U-boat losses, including many boats sunk on their first patrol, prompted the Germans to put more resources into training. Also, the Germans broke up existing veteran crews and dispersed the men amongst the U-boat fleet, so the crews of all newly commissioned boats would include a core of experienced, long-serving crewmen.<ref name="mulligan79" />

Months later, the German command was still trying to discover the fate of ''U-570''{{'}}s codebooks. A system of coded messages, hidden in the text of apparently ordinary, personal letters, was used to order Otto Kretschmer to report on this. They were unaware that the Allies had discovered this channel of communication with German prisoners.<ref>{{cite web |url=http://www.uboatarchive.net/POW/POWInternmentMail.htm|title=Letter from LCDR Albrecht visiting London to LCDR Rihheldaffer concerning Code used in POW mail|publisher=U-boat Archive |access-date=13 February 2010}}</ref>

==Royal Navy service==
[[File:Crew of HMS Graph IWM A 009888.jpg|thumb|right|alt=Around 15 men are drinking from white mugs at a table in a narrow compartment. They are surrounded by bunk-beds and machinery. The space is cramped and the men are packed closely together.|Some of the Royal Navy crew of ''Graph'' having supper in the forward torpedo room during sea-trials, February 1942]]
The disposition of ''U-570'' was initially uncertain. [[Winston Churchill]] was in favour of handing her over to the Americans for repair, both for propaganda and as a means of deepening then-neutral America's engagement in the [[Battle of the Atlantic]].<ref name="blair346" /> The Americans were eager to have her, but the Royal Navy objected both to this and to Churchill's other idea – to have her serve in the Mediterranean with a Yugoslav crew.<ref name="blair346" /> Instead, she was [[Ship commissioning|commissioned]] into the Royal Navy as HMS ''Graph'' on 5 October 1941, and assigned the Royal Navy pennant number P715. She was given a name beginning with a 'G' to signify ''German'', i.e., denoting that ''Graph'' was a captured vessel. The name Graph was also chosen owing to the extensive testing carried out on her (and therefore the many "Graphs" drawn up),<ref name="blair347" /> but was also a play on the [[German language|German]] word ''Graf'' meaning "Count".

===Trials===
[[File:A 009887.jpg|thumb|right|alt=A picture, taken through a round hatchway, shows a machinery filled compartment. A single man, wearing a dark uniform, is bending over a table, lit by a desk-light.|A Royal Navy Sub-Lieutenant works at the chart-table in the control room of ''Graph'', February 1942]]
Once seaworthy, meticulous trials were conducted to measure every aspect of ''Graph''{{'}}s sailing and diving characteristics. Even the [[Carl Zeiss AG|Zeiss]] binoculars found on board were carefully tested.

''Graph''{{'}}s safe diving depth was discovered to be {{convert|230|m|ft|-1}}—much deeper than the British thought for this kind of boat. At the time, Royal Navy depth charges had a maximum depth setting of {{convert|170|m|ft|-1}} so the Germans could dive out of their reach. Depth charges were soon modified to take account of this.<ref name="macintrie">{{cite book | title=U-Boat Killer: Fighting the U-Boats in the Battle of the Atlantic | last=Macintrie | first=Donnald | year=2004 | publisher=Rigel Publications | isbn=1-898799-78-4}}</ref> The boat's acoustic and magnetic characteristics were examined by different Admiralty research establishments.<ref>{{cite web|title=ADM 259/575—''Trials of captured U-boat HMS/M Graph''|year=1942|publisher=Royal Navy, now in [[The National Archives (United Kingdom)|The National Archives]]|url=https://www.nationalarchives.gov.uk/catalogue/externalrequest.asp?requestreference=ADM259/575}}</ref><ref>{{cite web|title=ADM253/436—''Magnetic field of captured German submarine U570 (HMS/M Graph)''|publisher=Mine Design Department and Mining Establishment, Royal Navy, now in [[The National Archives (United Kingdom)|The National Archives]]| year=1941| url=https://www.nationalarchives.gov.uk/catalogue/externalrequest.asp?requestreference=ADM253/436}}</ref>

The Allied technical experts found much to praise about her design and construction. ''Graph''{{'}}s auxiliary machinery was on rubber mountings, making her stealthier by reducing sound transmission into the hull.<ref>{{cite book | title=Cold War, Hot Science: Applied Research in Britain's Defence Laboratories, 1945–1990 | last1=Bud | first1=Robert | last2=Gummett | first2=Philip | year=2002 | page=166 | publisher=NMSI Trading Ltd | isbn=1-900747-47-2}}</ref> The British and the Americans who examined ''Graph'' singled out her Zeiss periscope for particular praise. The American officers who carried out her initial inspection in Iceland recommended it be copied as quickly as possible for possible US Navy use.<ref>Report On The German Submarine U-570 Class p.37</ref> Her underwater acoustic equipment was found to be a sophisticated array of [[hydrophone]]s that was significantly better than the British equivalents.<ref name="blair346">Blair 1996, p. 346.</ref> The main criticism of the boat was poor and cramped crew accommodation, which would degrade crew performance on long patrols.

In mid-1942, ''Graph'' was carefully studied by the US Navy, which then had an interest in a new, smaller submarine that would be roughly her size – around two-thirds the length and half the displacement of the [[Gato class submarine|''Gato''-class]] boats that formed the bulk of the US submarine fleet. She was considered superior in many ways to the two experimental [[Mackerel class submarine|''Mackerel''-class]], the existing class of small US submarine, but the project was dropped.<ref>{{cite book |title=U.S. submarines through 1945: an illustrated design history |last=Friedman |first=Norman |year=1995 |publisher=Naval Institute Press |isbn=1-55750-263-3 |page=229 }}</ref>

Full-scale models of her pressure hull were constructed, and used during mid-1942 for underwater tests of experimental [[shaped charge]] anti-submarine bombs.<ref>{{cite web | url=http://www.iwm.org.uk/collections/item/object/30023796 | title=Bomb Anti Submarine 35 lb Hollow Charge | publisher=Imperial War Museum | work=Collections and Research | access-date=23 February 2012}}</ref> In a highly secret British project, ''Graph'' was also used as a model for the construction of three, full-sized, mock-ups of the control compartment, wardroom and radio room of a Type VII U-boat. These were used to train specialist groups of sailors, who would form boarding parties whenever a damaged U-boat was blown to the surface. They were trained to operate a U-boat's ballast-tank valves, to reverse any scuttling attempts by the crew, and to search quickly for cryptographic equipment and documents.<ref name="blair347" /><ref>{{cite web| url=https://www.nationalarchives.gov.uk/catalogue/externalrequest.asp?requestreference=ADM1/11826| title=ADM 1/11826—''NAVAL TRAINING (54): Control room of U570 (later HMS/M GRAPH): construction by Vickers-Armstrong for training boarding parties''|publisher=Royal Navy, now in [[The National Archives (United Kingdom)|The National Archives]]}}</ref>

===Active service===
After completing trials under the command of Lieutenant Commander E.D. Norman, ''Graph'' was placed under the command of Lieutenant Peter Barnsley Marriott, who had assisted in the trials. She departed from [[Holy Loch]] for her first Royal Navy war patrol on 8 October 1942, with the intention of patrolling the [[Bay of Biscay]].<ref name="uboatdotnet-graph">{{cite web | url=https://uboat.net/allies/warships/ship/7751.html | title=HMS Graph (P 715) | publisher=uboat.net | work=Allied Warships | access-date=26 February 2012}}</ref>
[[File:The Submarine Hm Graph - Ex-u-boat 570. 20 April 1943, Holy Loch, the German Submarine U 570 Which Was Captured and Renamed HMS Graph. in 1941 a Hudson Aircraft Forced the U-boat To Surrender on the Surface, Un A16044.jpg|thumb|''Graph'' at [[Holy Loch]], Scotland, after she had ceased active service and been reassigned for training use (20 April 1943)]]

On the afternoon of 21 October 1942, about {{convert|50|nmi|-1}} north-north-east of [[Cape Ortegal]] ({{coord|44|31|N|7|25|W}}), ''Graph'' dived to evade a German [[Focke-Wulf Fw 200]] long-range patrol aircraft. A loud hydrophone contact made Marriott believe a nearby submarine had likewise dived and, 12 minutes later, he observed its conning-tower against the setting sun. After pursuing the German boat, ''Graph'' fired four torpedoes. Explosions were heard, and also banging noises, leading the British to believe they had hit the other submarine and the banging noises were caused by her breaking up as she sank.<ref name="Terrell-146">Terrell (1958), p. 146</ref> In early 1943, Marriott was awarded the [[Distinguished Service Order]] for "great courage, skill and determination in a successful submarine patrol".<ref>{{London Gazette|issue=35851 |supp=y|page=173|date=1942-01-05}}</ref>

After the war, examination of German records showed the submarine attacked was the {{GS|U-333||2}}, badly damaged after being rammed by the [[Flower-class corvette]] HMS ''Crocus'' off the coast of West Africa. German lookouts had seen the torpedoes' tracks, enabling ''U-333'' to evade the torpedoes;<ref>{{cite web | url=http://www.rnsubs.co.uk/Dits/Articles/U333.php | title=How flower power beat a U-Boat in the Atlantic | publisher=Barrow Submariner's Association | access-date=2013-06-26 | archive-url=https://web.archive.org/web/20131004224516/http://www.rnsubs.co.uk/Dits/Articles/U333.php | archive-date=4 October 2013 | url-status=dead }}</ref> the torpedoes then self-detonated for unknown reasons.<ref name="Terrell-146" /> The commander of ''U-333'' was [[Peter-Erich Cremer]]. In his post-war account of the attack, he suggested the rattling and banging noises ''Graph''{{'}}s crew had heard were due to the severe damage previously inflicted on ''U-333''. His route back to France closely hugged the Spanish coastline, a pattern followed by other U-boats, and he had also believed that Marriott was aware of this and had been lying in wait.<ref>Cremer (1984), p.110</ref>

''Graph's'' second war patrol was from 19 November 1942 to 8 December 1942, also in the Bay of Biscay. During the patrol, she was ordered to intercept the Italian cargo ship ''Cortellazzo'', which was passing through the area ''en route'' from Bordeaux to Japan with a cargo of 2000 tons of machinery. However, ''Graph'' failed to find the ship and the patrol was without incident.<ref name="uboatdotnet-graph" /> ''Cortellazzo'' was sunk within days by [[HMS Redoubt (H41)|HMS ''Redoubt'']], one of the destroyer escorts of an Allied troop convoy, after ''Redoubt'' had ordered ''Cortellazzo''{{'}}s crew to abandon ship and had picked them up.<ref>{{cite web | url=https://www.navyhistory.org.au/hmas-quickmatch-takes-a-prize/ | title=HMAS Quickmatch Takes a Prize | work=Naval History Society of Australia | access-date=12 May 2014 | author=Gladstone, Lieutenant G.V.| date=30 September 1974 }}</ref>

''Graph'' departed from [[Lerwick]] on her third war patrol on 24 December 1942 with three other Royal Navy submarines; their task was to patrol the waters off the coast of Norway in the area of [[Altafjord]]. At 1{{nbsp}}am on 1 January 1943, at the position {{coord|70|51|N|21|56|E}}, she sighted the German heavy cruiser [[German cruiser Admiral Hipper|''Admiral Hipper'']], returning from the unsuccessful attack on [[convoy JW 51B]], better known as the [[Battle of the Barents Sea]]. ''Hipper'' was too far off and travelling too fast to be attacked.<ref name="Terrell-147">Terrell (1958), p. 147</ref> At 4:23{{nbsp}}am, ''Graph'' sighted two German destroyers moving erratically and at low speed.<ref name="uboatdotnet-graph" /><ref group=Note>Six German destroyers took part in the Battle of the Barents Sea; one was sunk.</ref> ''Graph'' closed to a range of {{convert|7000|yd|m}} and fired four torpedoes. Again, explosions convinced the British that hits had been scored and a destroyer probably sunk, but again all the shots had missed.<ref name="uboatdotnet-graph" /><ref name="Terrell-147" /> ''Graph'' returned to Lerwick on 13 January 1943.

''Graph'' undertook no further war patrols. In 1943, she was assigned for training duties and command of her passed to Lt. D. Swanston.<ref name="uboatdotnet-graph" /> Peter Marriott went on to command {{HMS|Stoic}}, where he was awarded a [[Distinguished Service Cross (United Kingdom)|DSC]].{{refn|After the war ended, Marriott commanded a second U-boat, the surrendered ''U-776'', during a lengthy tour of British ports, when she was displayed to the public in order to raise money for the [[King George's Fund for Sailors]].<ref>Peterson (2012)''.</ref>|group=Note}}

===Decommissioning===

[[File:U-570 War ensign.jpg|thumb|right|U 570's ''[[Reichskriegsflagge]]'' or war ensign, displayed in the [[Royal Air Force Museum London]], 2023]]
Defects, exacerbated by a shortage of spare parts, led to ''Graph'' being placed in reserve. Also, her batteries and her [[MAN SE|MAN]] [[diesel engine]]s had a comparatively short service life; German submarine batteries required annual replacement, unlike British batteries, which were intended to last for the lifetime of the boat.<ref name="RCAHMS" />

She was decommissioned from active service on 21 June 1943. She saw some use as a target, to determine the damage caused by depth charges in full-scale trials.<ref>{{cite book |title=Submarines at War 1939–45 |last=Compton-Hall |first=Richard |year=2004 |publisher=Periscope Publishing Ltd. |isbn=1-904381-22-7 |page=69 }}</ref> After surviving these experiments, she was to be towed by the [[Admiralty tug|Royal Navy rescue tug]] HMRT ''Growler'' from [[Chatham Dockyard|Chatham]] to the [[River Clyde|Clyde]] for scrapping. But on 20 March 1944 her tow–rope broke in gale-force winds<ref name="Terrell-147" /> and, driven by wind and waves, she ran aground at a position {{coord|55|48|06|N|6|28|30|W}}, near Coul Point, on the west coast of [[Islay]], Scotland. ''Growler'' was unable to re-float the submarine and she was abandoned.<ref>Terrell (1958), p.148</ref>

''Graph'' was partially salvaged and scrapped in 1961. In 1966, the salvage diver [[Keith Jessop]] and others removed some more of the wreck, without the permission of the owner of the wreck's salvage rights; they paid £400 in compensation to the owner, but were still prosecuted and fined £50.<ref>{{cite book | title=Goldfinder | last1=Jessop | first1=Kieth | last2=Hanson | first2=Neil | year=2001 | pages=[https://archive.org/details/goldfindertruest00keit/page/102 102–104] | publisher=John Wiley and Sons | isbn=0-471-40733-X | url=https://archive.org/details/goldfindertruest00keit/page/102 }}</ref> Some remains of HMS ''Graph'' still remained visible at low tide on the rocks near Saligo beach in 1970, with the pressure casing of the conning tower and periscope tube visible (the cladding, railings and other parts had all broken off in the Atlantic storms many years before).<ref name="RCAHMS">{{Historic Environment Scotland|cat=PLA |num=102623 |num2=NR16NE 8002 |desc=Hms/M Graph: Campa, Islay, Atlantic |access-date=2025-06-19}}</ref> Today, the remains of the wreck lie in about {{convert|5|m|ft|-1}} of water;<ref name="RCAHMS" /> the site has been visited and photographed by recreational divers.<ref>{{cite web |url=http://www.wrecksite.eu/imgBrowser.aspx?13052 |title=U-570 |author=Carl Racey|date=6 October 2011 |publisher=www.wrecksite.eu}}</ref>

One of the ''Kriegsmarine'' battle flags of ''U-570'' was presented to Squadron Leader Thompson and is now part of the collection of the [[RAF Museum]]. Other surviving relics from the boat include her typewriter, held by the museum at [[Bletchley Park]],<ref name="Mallmann">{{cite book | title=Enigma U-Boats | last=Mallmann-Showell| first=Jak | year=2000 | page=87 | publisher=Ian Allan Publishing | isbn=0-7110-2764-1}}</ref> a small [[celestial globe]] used for navigation, that is owned by a private collector,<ref>{{cite web |url=http://www.atlantik-pirat.com/Gallery1.htm |title=The Gallery |date=6 October 2011 |website=www.atlantik-pirat.com |access-date=12 October 2011 |archive-url=https://web.archive.org/web/20120425062037/http://www.atlantik-pirat.com/Gallery1.htm |archive-date=25 April 2012 |url-status=dead }}</ref> and a German sailor's cap, that was taken as a souvenir by one of the officers of HMCS ''Niagara'' and is in the [[Canadian War Museum]].<ref>{{cite web |url=http://www.warmuseum.ca/cwm/exhibitions/navy/objects_photos_search-e.aspx?section=4-B&id=40&page=1 |title=Uniforms and Insignia U-570 Sailor's Cap |date=6 October 2011 |publisher=Canadian War Museum}}</ref> Another battle flag is claimed to have come into the possession of a young apprentice fitter at the Vickers Barrow shipyard and still survives.<ref>{{cite web |url=http://www.rnsubs.co.uk/Boats/BoatDB2/index.php?BoatID=718 |title=Graph (P715) |author=Myers, Bill |work=Boat Database: Graph |publisher=Submariner's Association, Barrow–in–Furness Branch |access-date=13 November 2012 |archive-url=https://web.archive.org/web/20130516015611/http://www.rnsubs.co.uk/Boats/BoatDB2/index.php?BoatID=718 |archive-date=16 May 2013 |url-status=dead }}</ref><ref group="Note">While it is quite possible the apprentice fitter was the volunteer who cut the torpedoes free and the flag was his reward, the sources do not explicitly confirm this.</ref>

==See also==
* [[List of submarines of the Second World War]]
*{{HMS|Meteorite}} – Formerly, the experimental, [[German Type XVII submarine]] ''U-1407''; used by the Royal Navy post-war.
*{{HMS|Seal|N37}} – Royal Navy submarine, captured and taken into service by the Germans.
*{{ship|HM Submarine|X2}} – Italian submarine captured and taken into service by the Royal Navy.
*{{GS|U-1105||2}} – German Type VII-C/41 U-boat that was [[Ship commissioning|commissioned]]  as the Royal Navy submarine ''N2'' between 1945 and 1946.

==Notes==
{{reflist|group=Note|colwidth=60em}}

==References==
{{Reflist}}

==Bibliography==
{{Refbegin}}

* [https://www.nationalarchives.gov.uk/catalogue/externalrequest.asp?requestreference=ADM186/806 "ADM 186/806—CB 4051 ''U 570, Interrogation of Crew''"], Intelligence Division Naval Staff, Admiralty. January 1941. Now in [[The National Archives (United Kingdom)|The National Archives]] and [http://www.uboatarchive.net/U-570/U-570INT.htm reproduced in full] by uboatarchive.net
*{{citation |title=ADM 239/358—CB 4318 ''Report on ex-German Submarine "U570" (HMS "Graph")'' |publisher=Intelligence Division Naval Staff, Admiralty |date=January 1943 |url=http://www.uboatarchive.net/U-570/U-570BritishReport.htm |quote=reproduced at uboatarchive.net|access-date=11 April 2017}}
*{{cite book | title=Hitler's U-Boat War: The Hunters 1939–42 | last=Blair | first=Clay | year=1996 | publisher=Random House |location=New York| isbn=0-394-58839-8}}
*{{cite book | title=Hitler's U-Boat War: The Hunted 1942-45 | last=Blair | first=Clay | year=1999 | publisher=Weidenfeld & Nicolson | isbn=0-297-84077-0}}
*{{cite book | title=Ultra Versus U-Boats: Enigma Decrypts in the National Archives | publisher=Pen & Sword Military | author=Conyers Nesbit, Roy | year=2008 | isbn=978-1844158744}}
*{{cite book | title=U333: Story of a U-boat Ace | last=Cremer | author-link=Peter-Erich Cremer | first=Peter | year=1984 | publisher=The Bodley Head Ltd | isbn=0-370-30545-0}}
*{{cite book | title=The Führer Led But We Overtook Him | last=Durham | first=Phil | year=1996 | publisher=Pentland |location=Edinburgh | isbn=1-85821-365-7}}: The memoir of a Royal Navy submariner who served on ''Graph''
*{{cite book | title=In Great Waters: The Epic Story of the Battle of the Atlantic | last=Dunmore | first=Spencer | year=2001 | publisher=Pimlico | isbn=0-7126-6932-9}}
*{{cite book |title=Secret Naval Investigator |last=Lincoln|first=Ashe |year=1961 |publisher=William Kimber and Co Ltd.|location=London }}: See chapter VIII in which the author describes joining Lieutenant Martin Johnson at Barrow to work out how to access the torpedoes.
*{{cite book |title=Neither Sharks Nor Wolves|last=Mulligan|first=Timothy |year=2011 |publisher=Naval Institute Press|isbn=978-1591145462}}
*{{cite web |title=Report On The German Submarine U-570 Class Captured By The British in August 1941 | url=http://www.uboatarchive.net/U-570/U-570ONIReport.htm| publisher=[[United States Navy]], reproduced by uboatarchive.net| date=28 September 1941 |access-date=11 April 2017}}
*{{cite news | url=https://www.shetlandtimes.co.uk/2012/04/09/from-london-to-lerwick-the-final-voyage-of-u-776 | title=From London to Lerwick: The final voyage of U-776 | work=The Shetland Times | date=9 April 2012 | access-date=2013-04-28 | author=Peterson, John}}
*{{cite book |title=Enigma: The Battle for the Code |last=Sebag-Montefiore |first=Hugh |author-link=Hugh Sebag-Montefiore |year=2000 |publisher=Weidenfeld & Nicolson |location=London |url=https://archive.org/details/enigmabattleforc0000seba |isbn=0-297-84251-X |url-access=registration }}
*{{cite book | last=Terrell | first=Edward | author-link=Edward Terrell|title=Admiralty Brief: the Story of Inventions that Contributed to Victory in the Battle of the Atlantic | publisher=Harrap | location=London| year=1958 | oclc=504731245}}
{{refend}}

==External links==
{{Sister project links|auto=y}}
* [https://web.archive.org/web/20070814061819/http://www.oca.269squadron.btinternet.co.uk/history/squadron_history/appendices/D_U_570/weisse_flagge.htm ''Weisse Flagge''], 269 Squadron RAF Website. A 1956 article from the German magazine ''Kristall'', translated by Gerry Raffé. Includes an account of Bernhard Berndt's prison camp escape and Rahmlow's own description of the circumstances of the boat's surrender.
* [https://web.archive.org/web/20070814061819/http://www.oca.269squadron.btinternet.co.uk/photo_gallery/u-570/U-570.htm U-570] 269 Squadron RAF Website, Pictures of the U-570's capture and her beaching at ?orlákshöfn.
*{{Cite web
 |url=https://uboat.net/boats/u570.html
 |title=The Type VIIC boat U-570
 |last=Helgason
 |first=Guðmundur
 |website=German U-boats of WWII - uboat.net
 |access-date=28 December 2014
}}

{{coord|55|48|06|N|6|28|30|W|region:XZ_type:landmark|display=title}}

{{German Type VII submarines}}
{{August 1941 shipwrecks}}
{{March 1944 shipwrecks}}

{{DEFAULTSORT:Graph (P715)}}
[[Category:Ships built in Hamburg]]
[[Category:German Type VIIC submarines]]
[[Category:Captured U-boats|German submarine U-570]]
[[Category:Submarines of the Royal Navy]]
[[Category:U-boats commissioned in 1941|German submarine U-570]]
[[Category:World War II submarines of Germany|German submarine U-570]]
[[Category:1941 ships]]
[[Category:Naval ships of Germany captured by the United Kingdom during World War II]]
[[Category:Maritime incidents in August 1941]]
[[Category:Maritime incidents in March 1944]]